The proposed project will use the Psychoses Register and other data resources at the institute of Public Health of the Socialist Republic of Croatia in Yugoslavia to establish a family data bank with high-density pedigrees, affected sib-pairs, and other pairs, of affected relatives with schizophrenia for the purpose of conducting DNA marker linkage studies. In this application for an initial three-year period, we are proposing (1) to screen the Psychoses Register and supporting files to identify schizophrenic probands with affected family members and to establish the family data bank on a PC, (2) to train the Yugoslavian Co-investigators and other clinicians who will be conducting diagnostic interviews in the use of structured interviews and ratings according to DSM-IIIR and the RD C. (3) to conduct diagnostic interviews and collect blood samples from approximately 490 individuals (schizophrenic probands and their relatives), (4) to begin work-up of the blood samples in the Molecular Genetics Laboratory, Department of Medical Genetics, New York State Psychiatric institute, immortalize cell lines, and begin the assay of DNA markers (candidate genes, chromosome 5 probes, etc.), and (5) to begin in preliminary linkage analyses according to any of several methods, as appropriate to the family structures that are identified.